Three-dimensional highly elastic film/non-woven composite

ABSTRACT

A three-dimensional highly elastic film/non-woven composite having a fluid and air impervious core layer and a first and second consolidated layer. The consolidated layers have unidirectional and non-unidirectional fibers. The composite is formed by laminating the air and fluid impermeable elastic core layer between the two layers of consolidated non-wovens. The resulting composite stretches only in the cross-machine direction due to the unidirectional properties of the consolidated non-woven material. The layers are then point bonded or welded together. Preferably the layers are welded by passing the composite between an ultrasonic horn and an ultrasonic bond roll having raised areas for effecting the weld points. A thin inelastic membrane is formed at each of the weld points. The welded composite may then be pre-stretched to rupture the membranes, thereby creating apertures, which makes the composite permeable.

BACKGROUND OF THE INVENTION

[0001] 1. Field of the Invention

[0002] The invention relates generally to film/non-woven composites andspecifically, to a point bonded highly elastic film/non-woven compositethat is made breathable after manufacture by stretching the composite torupture inelastic membranes formed on the composite by weld points usedto point bond the composite.

[0003] 2. Related Art

[0004] There is a need to improve the fit and comfort of diaper productsand the like in the consumer disposable market. Laminates that deliverhigh extensibility coupled with high elastic recovery, breathability,and tear resistance are being sought as the means to satisfy this need.

[0005] In the past, techniques used to achieve high stretch in non-wovenlaminates would often damage the non-woven fibers or bonds, therebyresulting in reduced laminate strength,-especially tensile strength. Inaddition, the laminates produced by prior techniques often lacksufficient elastic recovery to function optimally in desiredapplications.

[0006] Breathability for these laminates have typically been generatedby perforating the film before laminating the film to the non-woven. Thelamination of the film to the non-woven are often performed by the useof adhesives. These adhesives have a tendency to block the holes orapertures in the laminates, thus potentially reducing desiredbreathability.

[0007] Breathability was also generated by perforating the film throughother perforation processes, such as perforating the film afterlaminating the film to the non-woven. But these perforation processesresult in various points of weakness on the overall laminate. The pointsof weakness often become tear initiation points.

[0008] In the prior art, often many cumbersome and expensive steps mustbe followed to create a laminate having the desired properties.

[0009] Therefore it is necessary to develop a laminate and a method formaking the same that has high elasticity combined with high elasticrecovery for use in disposable article market. In addition, it isdesirable to develop a laminate and a method for making the same thateliminates the tear initiation points that formed on prior artlaminates. There is a further need to make a laminate having arelatively high tear resistance at a predetermined stretch elongation ofthe laminate. Finally, there is a need to reduce the number of stepsneeded to create the laminate while maintaining the above-statedproperties.

SUMMARY OF THE INVENTION

[0010] The present invention provides an improved film/non-wovencomposite that only stretches in the cross-machine direction andexhibits fluid and air permeable properties. The film/non-wovencomposite in one embodiment of the present invention comprises twoconsolidated layers laminated onto a core layer. The consolidated layersare composed of unidirectional and non-unidirectional fibers. Theunidirectional and non-unidirectional fibers provide for stretchable andnon-stretchable regions on the composite.

[0011] The layers of the composite are welded together at discretepoints. In one embodiment, an ultrasonic horn is used to weld thecomposite. After welding, the following distinct regions are formed onthe composite: non-welded regions, bond regions, and membrane regions.The non-welded regions are the areas of the composite surrounding theweld points. The weld points, where an actual bond forms, areamalgamated masses of polymer that are dislodged by force andthermal/fusion energy during the welding step. The membrane regions arevery thin impervious membranes of polymer material that remain after thethermal/fusion energy application.

[0012] After the composite has been formed, some areas of the compositeexhibit high elasticity. The composite may be stretched by an end userto tear the membranes in the membrane region and impart breathability tothe film. The ratio of tensile to break in the machine direction versusthe tensile to break in the cross direction of the fibers in theconsolidated layers is approximately 1.8:1.

BRIEF DESCRIPTION OF THE DRAWINGS

[0013]FIG. 1 is a cross-section of the film/non-woven composite of thepresent invention before the welding step.

[0014]FIG. 2 is a top view of the film/non-woven composite of thecomposite of FIG. 1 after the welding step.

[0015]FIG. 3 is a cross-section of the composite of FIGS. 1 and 2 takenalong line 3-3 of FIG. 2 after the composite has undergone the weldingstep.

[0016]FIG. 4 is a view of the film/non-woven composite of FIGS. 1 and 3undergoing the welding step.

[0017]FIG. 5 is a graph showing the relationship of the force versusextensibility of consolidated and non-consolidated film/non-wovencomposites.

[0018]FIG. 6 is a graph showing the relationship of the force to stretchconsolidated and non-consolidated composite versus the number of holes(apertures)generated.

DETAILED DESCRIPTION OF THE DRAWINGS

[0019] Referring to FIG. 1 there is shown a three-dimensional, highlyelastic film/non-woven composite 10 that has high extensibility and alow modulus of elasticity. The composite 10 includes a firstconsolidated sheet 12, a second consolidated sheet 14, and an imperviousfilm core layer 16. The consolidated sheets are composed of a spunbondfibers 18 (FIG. 2). Spunbond fibers 18 may be non-woven bicomponent orblended fibers. If the spunbond fibers 18 are bicomponent fibers, thecomponents of the fibers 18 preferably have two distinct meltpoints.Similarly, if the sheets 12 and 14 are comprised of blended fibers, itis preferred that the blended fibers have two distinct melt points.Preferably, spunbond fibers 18 have a weight of around 15-30 gsm. Thefilm core layer 16 may be of various materials, but the materials mustbe impervious to fluid and air. In one embodiment, the core layer 16 maybe comprised of a multi-layer film. Alternate elastomeric films may alsobe used as the core layer 16, such as a single layer elastomer, or afoam layer, but such films must be comprised of fluid and/or airimpervious materials.

[0020] In another embodiment, the core layer 16 is a highly-elasticcompound, such as a compound involving at least one or more blockco-polymers with a hydrogenated diene from the type A-B-A or A-B-A′.Usually such a compound exhibits relatively good elastic recovery or lowset from stretching over 100 percent when extruded alone as a singlelayer. Styrene/isoprene, butadiene or ethylene-butylene/styrene (SIS,SBS, or SEBS) block copolymers are particularly useful. Other usefulelastomeric compositions for use as an core layer 16 can includeelastomeric polyurethanes, ethylene copolymers, such as ethylene vinylacetates, ethylene/propylene copolymer elastomers orethylene/propylene/diene terpolymer elastomers. Blends of these polymersalone or with other modifying elastic or non-elastomeric materials arealso contemplated being useful with the present invention. In certainpreferred embodiments, the elastomeric materials can comprise highperformance elastomeric material such as SEBS, SBS, SIS or Kraton™elastomeric resins from the Shell Chemical Co., which are elastomericblock copolymers.

[0021] To form the film/non-woven composite 10, first and second sheetsof spunbond fibers 18 are oriented in an oven or other heating apparatusaccording to the teachings described in U.S. Pat. No. Re. 35,206 toHassenboehler, Jr., et al., which is incorporated herein by reference.The result of this process is first consolidated sheet 12 and secondconsolidated sheet 14. The individual fibers 18 are closely packed onthe sheets 12, 14 and stretch only in the cross-machine direction (i.e.,anisotropic fibers). The elastic film/non-woven composite 10 (FIG. 1) iscreated by encapsulating the core layer 16 between the consolidatedsheets 12, 14.

[0022] A combination of force and thermal/fusion energy, such asultrasonic welding or thermal contact welding, is used to combine thethree layers 12, 14, 16 at discrete weld points 20 to form weldedfilm/non-woven composite 21. (FIGS. 2 and 3 ). In a preferred embodimentshown in FIGS. 2 and 3, ultrasonic welding is used to form weld points20 that join the consolidated layers 12, 14 and the impervious film corelayer 16. The weld points 20 occupy between about 2% to about 10% of thetotal surface area of the film/non-woven composite 21. It has been foundthat weld points 20 having a diameter of approximately 0.75 mm andspaced in the cross-machine direction from centerline-to-centerlineapproximately 3.5 mm apart are desirable. Ultrasonic welding is thepreferred method of forming weld points 20. Other suitable methods maybe used, including thermal contact welding and point welding to create aweld points 20. A welded membrane 22 and a bond region 24 of materialresult from the application of weld points 20 as best seen in FIG. 3.Welded membranes 22 are very thin impervious membranes of polymermaterial that remain after the weld point application. The membranes 22are essentially non-elastic. After welding, first and secondconsolidated sheets 12 and 14 and the impervious film core layer 16comprise three regions. Non-welded regions 26 are the areas of thecomposite 21 surrounding the bond regions 24. Bond regions 24, where theactual bond forms, contain amalgamated masses 25 of polymer that aredislodged by force and thermal/fusion energy during the weld pointapplication. The film-forming process is discussed in greater detailbelow.

[0023] Breathability of the welded elastic film/non-woven composite 21results from tearing of the membranes 22. Membranes 22 are torn whencomposite 21 is stretched. During stretching, the membranes 22 tearbecause the membranes are non-elastic. Breathability is imparted to thefilm/non-woven composite 21 by inducing stretching in the cross-machinedirection in the range of about 50% to about 200%. As an example, in thecase of a 50% induction of stretching, a 1 inch sample of composite 21becomes at least 1.5 inches long. Despite the stretching of composite 21and the tearing of the membranes 22, the film/non-woven composite 21provides sufficient resistance to forces, especially forces that causeelongation at the composite 21 greater than about 200%, to preventtearing of the film/non-woven composite 21. The stretching of thefilm/non-woven composite 21 may occur during use, such as when an endproduct is stretched by the consumer or user, or prior to use at themanufacturing site, using methods known in the art. These methodsinclude using a tentering frame, a bowed bar, or interdigitating rollssuch as those described in U.S. Pat. No. 4,368,565 to Schwarz, which isincorporated herein by reference.

[0024] Referring now to FIG. 4, the elastic film/non-woven composite 10is shown undergoing a welding processes to form weld points 20. Weldpoints 20 point bond or weld the consolidated sheets 12, 14 to theimpervious film core layer 16 to form welded elastic film/non-wovencomposite web 21. To perform ultrasonic welding, the elasticfilm/non-woven composite web 10 is passed between ultrasonic horn 30 andultrasonic bond roll 32. Ultrasonic bond roll 32 has a plurality ofraised areas 34. During ultrasonic welding, the mass of consolidatedlayers 12, 14 that are proximate to the raised area 34 of the ultrasonicbond roll 32 become molten and flow outward away from ultrasonic horn 30to form a weld point 20. The thin layer material that remains formsmembrane 22, which is surrounded by amalgamated masses 25 (FIG. 3).Membrane 22 remains impervious to fluid or air after welding. Thelocation of membrane 22 corresponds to the individual raised areas 34 ofthe bond roll 32, which provide the points for the ultrasonic bonding.Raised areas 34 do not completely penetrate film/non-woven composite 10but act as a primary channel for the energy force that is beingtransmitted from the ultrasonic horn 30. Without raised areas 34, theforce supplied by the horn 30 across the elastic film/non-wovencomposite web 10 would be uniform. As a result, the raised areas 34impart a pattern on welded film/non-woven composite 21.

[0025] The resulting welded film/non-woven composite 21 has highelasticity in the cross-machine direction, which is the directiontransverse to the direction that the composite 10 and resulting weldedcomposite 21 travel during the welding process shown in FIG. 4. Weldedcomposite 21 resists stretching in the machine direction, which isparallel to the direction the composite 10 and resulting weldedcomposite 21 travel during the welding process. The weldedfilm/non-woven composite 21 has a final weight in the range of about40-150 gsm.

[0026] After the welding process of the invention, apertures are createdin the film/non-woven composite 21 by stretching composite 21 to rupturemembranes 22 and the composite 21 is allowed to return to its originallength.

[0027] Experimental Description

[0028] The experiment described below has been set-up to demonstrate theimpact of imparting breathability on the properties of variouslaminates. The experiment has three steps:

[0029] 1. Laminate Creation step

[0030] 2. Laminate Activation steps

[0031] 3. Laminate Property Quantification step.

[0032] The laminate Creation Step involved the creation of three samplelaminates, sample A, sample B, and sample C. Sample A consists of anelastic film that is ultrasonically bonded and uses Softspan® nonwovenson both sides off the film. Sample B consists of an elastic film that isultrasonically bonded and covered on both sides by two layers of thesame Softspan® nonwovens as sample A. In addition, each of the Softspan®nonwoven layers was consolidated with a neck-in ratio of 2:1 beforebeing attached to each side of the film. Sample C is the same as sampleB except that each of the Softspan® nonwoven layers was consolidatedwith a neck-in ratio of 3:1 before being attached to each side of thefilm.

[0033] In the Laminate Activation or Hole Creation Step, holes werecreated in samples A, B, and C by stretching the samples to variouslevels and allowing them to return to their original length. In thisexperiment, the laminates were stretched by hand. Specifically, a 1 inchmark was made on each sample and the material was stretched to apredetermined extensions. The materials were then stretched variousamounts and the force required to stretch that amount was recorded.

[0034] Table 1, below, and FIG. 5 show a comparison of the stretchbehavior of samples A, B, and C after being pre-stretched to 100% each.The data indicates that consolidated samples B and C gained anadditional 100% extensibility as compared to the non-consolidated sampleA. The consolidated samples B and C required lower forces to stretch,particularly after 60% stretch. The higher force to stretch thenon-consolidated samples B and C imply that the actual fibers 18 arebeing deformed instead of stretching. The data supports the postulatethat higher deformation causes irreversible damage to the stretch matrixof the consolidated sheets. Additionally, the gain in higherextensibility by the consolidated samples B and C makes the sampleseasier, i.e. requires less force, to stretch the composite further ascompared to the non-consolidated sample A. TABLE 1 Neck-in Ratio SpeedInitial/ Ratio Basis TD ULT Ult. TD Final Final/ Temp. Width WT. TD 10%TD 25% TD 50% TD 100% force Elong. Sample Nwvn Width Initial Fahrenheitinches gsm grams/in grams/in grams/in grams/in grams/in % A Softpan ™1:1 1.00 RT 35.125 118.4 35 784 1147 1412 2290 277 B Softpan ™ 2:1 1.38260 F. 30.125 133.5 30 210 300 430 2306 441 C Softpan ™ 3:1 1.75 260F.22.125 142.1 39 209 264 308 2491 500

[0035] In the Laminate Property Quantification step, after the materialwas pre-stretched, the holes in each of the samples A, B, and C werecounted in an a predetermined area. Next, the forces to stretch thesamples in the cross machine direction and the ultimate elongation tobreak forces were measured.

[0036] Referring now to FIG. 6, the force to stretch versus the numberof apertures generated is illustrated. In the experiment, the Samples A,B and C of the welded film/non-woven composite 21 were stretched tocreate apertures or pre-stretched. The apertures in each of the SamplesA, B and C were then counted in a sample area to determine thepercentage of membranes 22 (FIG. 3) that ruptured. Additionally, theforces to stretch the film/non-woven composite 21 to 100% elongation inthe cross machine direction were measured.

[0037] By referring to FIG. 6, it can be seen that in non-consolidatedfilm/non-woven sample A, once a 48 % aperture level is reached, theoverall integrity of sample A begins to decay. Additionally, both of theconsolidated samples B and C experience no damage or change in theirmodulus properties at the 100% modulus level even though samples B and Cwere stretched until all of the membranes 22 had ruptured, i.e. 100%holes were created.

[0038] The data of FIG. 6 supports the conclusion that with aconsolidated film/non-woven composite (samples B and C), a very highpercentage of apertures may be imparted in the film/non-woven compositewithout damaging the network of fibers 18 or destroying thefilm/non-woven composite integrity. This is a great improvement over thepercentage of apertures that may be formed in a non-consolidatedmaterial before damage results to the material, e.g., sample A. Further,the consolidated film/non-woven samples B and C exhibited propertiesthat are clearly superior to other laminates or fabrics that have beenmade in the past and were strained to become breathable.

[0039] As will be appreciated by those skilled in the art, the variousparameters of this invention may be adjusted depending on theapplication, including varying the weight of the non-woven layers 12,14, the consolidation ratio of layers 12 and 14, and the selection ofthe polymers for use as the impervious core film layer 16 of the elasticfilm/non-woven composite web.

[0040] The crux of the invention is a breathable and permeableconsolidated film/non-woven composite formed by laminating an air andfluid impermeable elastic layer between two layers of consolidatednon-wovens and forming an air or fluid pervious thin structure that haswell-defined elasticity and selective regions of breathability withoutthe need for using a process or apparatus to impart apertures in thefilm. The resulting composite allows for the formation of a highpercentage of apertures from a given number of weld points by stretchingthe composite without damaging the structure of the composite.Additionally, the process of the invention may be practiced withoutusing excessive thermal or fusion energy force that may damage thespikes or raised areas of the embossing roll. Further, the resultingcomposite stretches only in the cross-machine direction due to theunidirectional properties of the consolidated non-woven material.

[0041] While only several embodiments of the present invention have beendescribed the present invention may also be applied to many otherapplications and environments. It will be obvious to those skilled inthe art that various changes and modifications can be made withoutdeparting from the spirit and scope of the present invention, and it isintended to cover the claims appended hereto. All such modifications arewithin the scope of this invention.

What is claimed is:
 1. A three-dimensional highly elastic film/non-woven composite, comprising: a fluid and air impervious core layer having a first side and a second side; a first consolidated layer point bonded by a plurality of weld points to said first side of said core layer; a second consolidated layer point bonded by a plurality of weld points to said second side of said core layer; and wherein said weld points are substantially inelastic.
 2. The three-dimensional highly elastic film/non-woven composite of claim 1, wherein: said core layer comprised of a material selected of a group consisting of an elastomeric film, a foam, and a multi-layer film.
 3. The three-dimensional highly elastic film/non-woven composite of claim 1, wherein: said first consolidated layer and said second consolidated layer are comprised of bicomponent fibers that have at least two distinct meltpoints.
 4. The three-dimensional highly elastic film/non-woven composite of claim 1, wherein: said first consolidated layer and said second consolidated layer are comprised of blended fibers that have at least two distinct meltpoints.
 5. The three-dimensional highly elastic film/non-woven composite of claim 1, wherein: said first consolidated layer and said second consolidated layer are comprised of unidirectional fibers and non-unidirectional fibers; and said first consolidated layer is comprised of fibers that are anisotropic.
 6. The three-dimensional highly elastic film/non-woven composite of claim 1, wherein: said first consolidated layer and said second consolidated layer are comprised of unidirectional fibers and non-unidirectional fibers; and said second consolidated layer is comprised of fibers that are anisotropic.
 7. The three-dimensional highly elastic film/non-woven composite of claim 1, wherein: said weld points occupy between about 2% to about 10% of a total surface area of the film/non-woven composite.
 8. The three-dimensional highly elastic film/non-woven composite of claim 1, further comprising: membranes formed in said weld points wherein said membranes rupture to form apertures when the composite is stretched in a transverse direction to an elongation greater than about 50%.
 9. The three-dimensional highly elastic film/non-woven composite of claim 1, wherein: the composite provides sufficient resistance to forces greater than about 1500 grams per inch to prevent tearing of the composite.
 10. The three-dimensional highly elastic film/non-woven composite of claim 1, wherein: the composite has an ultimate tensile direction elongation percentage in the range of about 400% to about 650%.
 11. The three-dimensional highly elastic film/non-woven composite of claim 1, further comprising: stretchable regions and non-stretchable regions.
 12. The three-dimensional highly elastic film/non-woven composite of claim 1, wherein: said first consolidated layer and said second consolidated layer are comprised of unidirectional fibers and non-unidirectional fibers; and said unidirectional and non-unidirectional fibers of said first consolidated layer have a tensile to break ratio in a machine direction to a cross direction in the range of about 3:1 to about 1.8:1.
 13. The three-dimensional highly elastic film/non-woven composite of claim 1, wherein: said first consolidated layer and said second consolidated layer are comprised of unidirectional fibers and non-unidirectional fibers; and wherein a tensile to break ratio for said unidirectional and non-unidirectional fibers in a machine direction to a cross direction of said first consolidated layer is about 1.8:1.
 14. The three-dimensional highly elastic film/non-woven composite of claim 1, wherein: said first consolidated layer and said second consolidated layer are comprised of unidirectional fibers and non-unidirectional fibers; and wherein a tensile to break ratio for said unidirectional and non-unidirectional fibers in a machine direction to a cross direction of said first consolidated layer is about 3:1.
 15. The three-dimensional highly elastic film/non-woven composite of claim 1, wherein: said first consolidated layer and said second consolidated layer are comprised of unidirectional fibers and non-unidirectional fibers; and wherein the tensile to break ratio for said first consolidated layer for a machine direction to a cross direction is about 1.8:1.
 16. The three-dimensional highly elastic film/non-woven composite of claim 1, wherein: the tensile to break ratio forces of said first consolidated layer in a machine direction to a cross direction is about 3:1.
 17. A three-dimensional highly elastic film/non-woven composite, comprising: a fluid and air impervious core layer having a first side and a second side; a first consolidated layer point bonded by a plurality of weld points to said first side of said core layer, said first consolidated layer having unidirectional fibers and non-unidirectional fibers, wherein said unidirectional and non-unidirectional fibers of said first consolidated layer have a tensile to break ratio for a machine direction to a cross direction in the range of about 3:1 to about 1.8:1; a second consolidated layer point bonded by a plurality of weld points to said second side of said core layer, said second consolidated layer having unidirectional fibers and non-unidirectional fibers; and a plurality of bond regions formed by said weld points that bond said first consolidated layer, said second consolidated layer and said core layer together; inelastic membranes within said bond regions, said membranes for tearing upon stretching of the composite, thereby forming apertures.
 18. The three-dimensional highly elastic film/non-woven composite of claim 17, wherein: the unidirectional fibers and non-unidirectional fibers have a tensile to break ratio of a machine direction to a cross direction in the range of about 3:1 to about 1.8:1, wherein the unidirectional fibers of said second consolidated layer are oriented in the same direction as the unidirectional fibers of said first consolidated layer fibers.
 19. A method for forming a three-dimensional highly elastic film/non-woven composite, comprising the steps of: laminating a first consolidated sheet to a first side of an air and fluid impermeable elastic core layer; laminating a second consolidated sheet to a second side of an air and fluid impermeable elastic core layer; and stretching the composite in the transverse direction to create apertures in said composite.
 20. The method of claim 19, further comprising the steps of: point bonding said first and said second consolidated layers to said core layer; and forming a substantially inelastic membrane by said step of point bonding.
 21. The method of claim 20, wherein: said step of point bonding said first and said second consolidated layers is achieved by ultrasonic welding.
 22. The method of claim 20, wherein: said step of point bonding said first and said second consolidated layers is achieved by a combination of force and thermal energy.
 23. The method of claim 20, wherein: said step of point bonding said first and said second consolidated layers is achieved by thermal contact welding.
 24. The method of claim 19, wherein: said step of stretching the composite in the transverse direction is performed by an end user of the composite.
 25. The method of claim 19, wherein: said step of stretching the composite in the transverse direction is performed by a tentering frame.
 26. The method of claim 19, wherein: said step of stretching the composite in the transverse direction is performed by a bowed bar on a roll.
 27. The method of claim 19, wherein: said step of stretching the composite in the transverse direction is performed by interdigitating rolls. 